In communication systems, such as radio paging systems, messages are transmitted to subscribers via pagers or other portable radio communication devices. Generally, a person subscribes for service in a particular geographic area by signing up with a service provider operating in the geographic area. The service provider then furnishes the subscriber with a pager for receiving messages. Subscriber information, i.e., a subscriber record, associated with the pager is entered by the provider into a "home" terminal so that specifications about the pager and about the needs of the subscriber can be utilized for messaging. The subscriber record can, for example, include a pager identification number (pager ID), addresses associated with the pager; types of messages, e.g., alphanumeric, tone only, voice, etc., associated with the different addresses, and billing information. Additionally, when the pager receives messages that are transmitted in the conventional FLEX.TM. signaling format, the subscriber record can store collapse values, a home frame, and frame offset values for messaging at different frequencies.
When arrangements have been made between different service providers, a subscriber can roam out of his usual geographic area into a different geographic area serviced by another provider and still receive messages. When someone calls into the local terminal associated with the new region and enters a message to be transmitted to the subscriber's pager, though, the local terminal cannot transmit the message immediately because it does not have the pager's address, home frame, frequency offset values, or message formats stored locally. Therefore, in a conventional system, the local terminal must request message validation by sending the request, along with the message, to all other service providers from which the subscriber could have roamed. The home terminal receives the request and the message and then formats the message according to the subscriber record associated with the roaming pager. The formatted message is returned to the local terminal. The home terminal must also send additional information, such as frequency offset values, collapse values, and the home frame assigned to the roaming pager. Once all of this information has been received by the local terminal, the message can finally be transmitted to the roamer.
Conventionally, this procedure occurs every time the local terminal receives a message for transmission to the roamer. This is a relatively inefficient process that can crowd the communication links between terminals and result in backlogs. Furthermore; the process is time consuming, resulting in delay of message reception for the roamer. When the roaming subscriber has a need to receive urgent messages, e.g., when the pager is carried by a doctor or a police officer, such delays can be critical.
Thus, what is needed is a method and apparatus for efficient roaming between communication systems.